a) Field of the Invention
The present invention is directed to a controllable microscope illumination within a microscope system by which all essential contrasting methods in microscopy can be realized.
b) Description of the Related Art
High-pressure lamps and halogen lamps are conventionally used in the prior art as microscope illumination. Because of deficient controllability with respect to brightness, color temperature and/or color, additional optical components such as filters, attenuators, and so on, are needed for controlling the output signal of the light source. Another essential feature is the given geometry of the light sources that are used which usually requires additional optics for shaping the light bundle. While all contrasting methods in microscopy can be realized by means of these light sources, the resources required for this purpose are usually considerable.
An illumination device for flexible configuration of standard illumination modes is described in U.S. Pat. No. 4,852,985 A. Semiconductor light sources such as, e.g., LEDs arranged in two dimensions are used as an illumination source. The different illumination modes are implemented by selectively switching on the required LEDs. In addition, a device can be provided for adjusting brightness. By selectively switching on a quantity of LEDs in this way, the different types of illumination in a microscope can be realized without additional optical components. The surface light source can also be formed by the two-dimensional arrangement of LEDs emitting different colors, e.g., red, green and blue (RGB). In order to generate the most uniform possible color impression in the object plane without color fringes, the arrangement of the individual colors on the array is of great importance. U.S. Pat. No. 4,852,985 A describes a variant for a defined arrangement of LEDs for a three-color array. In this solution, a ground glass disk arranged in front of the surface light source is required to prevent nonuniformities in the illumination. The disadvantage in the LED-based RGB illumination for microscopy according to the prior art consists in that the spectral distribution does not cover the entire visual area which is necessary for the color-correct representation of microscopic samples.
U.S. Pat. No. 6,369,939 B1 likewise describes an illumination device for a microscope which uses LEDs. Two light sources are arranged in the illumination beam path to achieve an optimized geometric light flux. The second light source is located in a central bore hole of the collector lens. The light of the first light source is focused in the object plane via diffusing screens and collector lenses. This type of illumination is used for objectives having a small field and a large aperture. In contrast, the second light source illuminates the object plane with a parallel beam bundle based on Köhler's principle. This type of illumination is used for objectives having a large field and a small aperture. Depending on the objective that is used, one light source or the other is used for illuminating the object plane. This solution has the drawback that the second light source is limited in size and therefore in intensity.
A transmitted light illumination unit for microscopes in which a transparent microscope stage is illuminated from below is described in DE 199 19 096 A1. The illumination unit which comprises one or more LEDs is constructed in such a way that it can be arranged in the aperture diaphragm plane and in front of Köhler illumination optics. To ensure an illumination which is as uniform as possible, suitable diffusing means are arranged in front of the LEDs.
EP 1 150 154 B1 describes an incident illumination for microscopes in which a ring carrier which is oriented around the optical axis is provided for receiving illumination means. In this case, light-emitting semiconductor diodes (LEDs) which are arranged in a plurality of concentric circles in the ring carrier are used as illumination means. The principal beam direction of the LEDs is directed to the optical axis. The longitudinal axes of the LEDs of a circle intersect at a point on or in the vicinity of the optical axis (system axis). The LEDs which are preferably constructed as white light diodes are controllable in groups and their brightness can be regulated. Dynamic illumination variants can also be realized with the described incident illumination.
Another incident illumination device is described in DE 103 39 619 A1. The incident illumination device is integrated in a surgical stereo microscope, the light generated by at least one LED being imaged in the object field coaxial to the microscope beam path via the main objective or additional illumination optics. Variants based on the Köhler principle as well as those based on non-Köhler principles can be implemented. White light LEDs or combinations of different colored LEDs, e.g., combinations of red, green and blue, can be used.
Also, WO 2004/086 117 A1 describes an arrangement for the illumination of objects with light of different wavelengths using LED light sources. A rotatable receiving device is provided with holders, each of which receives at least one LED. By rotating the receiving device, different LEDs are positioned in front of a light outlet opening. Also, white-light LEDs or combinations of different colored LEDs such as, e.g., combinations of red, green and blue can be used.
U.S. Pat. No. 5,489,771 A describes an LED light standard for photo- and videomicroscopy. In this calibration system, the intensity of a compact LED light source is controlled by means of a detector. A diffuser arranged in front of the LED light source ensures extensively homogeneous light and also ensures that a portion of the light radiation strikes the laterally arranged detector and can be evaluated. In this standard light source which is usable for calibration, the generated light intensities can be adjusted very exactly in that the energy supplied to the LEDs can be compensated continuously via the regulating circuit with the detector. The compact LED light source preferably comprises LEDs which emit different colors (RGG or RGB) and which can be controlled individually. A monochrome light can be generated by selectively controlling the LEDs and through the use of bandpass filters. It is necessary to synchronize the camera and/or video camera in a corresponding manner when generating pulse-modulated light.